The Eddington Ratio Distribution of Narrow-line Active Galactic Nuclei

Abstract

We measure the Eddington ratio distribution of local optical narrow-line active galactic nuclei (AGN) as a function of host galaxy properties, as a potential test of galaxy formation theories of AGN feedback. We extract central emission-line fluxes using data from the Mapping Nearby Galaxies at APO (MaNGA) sample of the Sloan Digital Sky Survey IV Data Release 17. Using the line ratio diagnostic techniques of X. Ji & R. Yan, we identify AGN galaxies and determine their Hβ and [O iii] line luminosities. For all galaxies not identified as AGN, we determine the threshold line luminosity they would have needed to be identified as AGN. These luminosity thresholds allow us to account for selection effects that otherwise would lead to strongly biased results. From the Hβ luminosities and luminosity detection thresholds, accounting for selection effects, we measure the luminosity and Eddington ratio distributions of Seyferts as a function of specific star formation rate (sSFR) and stellar mass. Defining FAGN as the occurrence rate of AGN above a fixed Eddington ratio of 10−3, we find that FAGN is constant or increasing with stellar mass for star-forming galaxies and declines strongly with stellar mass for quiescent galaxies. At stellar masses (Formula presented) log10M*>10.25, the occurrence rate increases monotonically with sSFR. At low statistical significance, in our lowest mass bins (Formula presented) 9.25 <10.25, FAGN peaks at intermediate sSFR. These patterns reveal a complicated dependence of AGN activity on galaxy properties for theoretical models to explain.